1. Field of the Invention
The present invention relates to a video processing technique, and in particular to a technique for automatically assigning virtual camera operations to video.
2. Description of the Related Art
The recent ubiquity of digital still cameras and digital video camcorders has made frequent opportunities for still-image and video capturing. In addition, increasing storage capacity has increased the number of contents therein dramatically. Meanwhile, such contents have been viewed by reproducing and displaying a slide show or images in full screen on a display apparatus.
With the increase in the number of contents, there is a strong need for a viewing environment that enables automatic editing of output video. Thus, recently, some slide shows have started to use display effects obtained by cropping multiple parts of an image and displaying the cropped parts as video in cropped order so that a still image is viewed like a live-action moving image.
However, many of such display effects are uniform and have not yet satisfied many viewers. Also, the editing of a moving image requires special skills and takes a long time. There is also an editing system that is known to automatically determine areas to be cropped for each frame in a moving image and reproduce video with more dramatic video effects, but in fact, such editing is in many cases not performed as viewers would have desired. In particular, as for a section of video that is almost unchanged, there is little information that can be used as a guide for editing, so viewers are restricted to view monotonous images.
For example, in the configuration described in Japanese Patent No. 03793142, for the editing of assigning a virtual camera operation by cropping area spaces in accumulated video, areas to be cropped are determined by setting restrictions such as not being allowed to go out of frame, having a specified resolution or higher, and being allowed to move at a speed only within a specified range. Areas to be cropped are determined by using image feature quantity, sound feature quantity, and any other metadata on video reproduction or distribution. In particular, an area where an object exists is used as the image feature quantity.
Meanwhile, Japanese Patent Laid-Open No. 2006-309661 describes a configuration in which the number of subjects and the sizes of people's faces are identified in a still-image slide show, and if the number of subjects is larger than a threshold, multiple areas are cropped and output so as to include not more than an arbitrary number of subjects.
However, in the configuration described in Japanese Patent No. 03793142, depending on the contents of video, in particular in such a case where subjects remain almost stationary, the same area spaces are cropped, and monotonous video reproduction is forcefully issued accordingly. Also, in Japanese Patent Laid-Open No. 2006-309661, not only cannot a natural camera operation such as zooming, panning, or tilting be expected, but also image continuity is degraded. For example, if the display technique described in Japanese Patent Laid-Open No. 2006-309661 is applied to an image in which subjects are aligned, it is difficult to grasp the relationship of the order of the subjects from a displayed image.